Steam-heated apparatus



May 13, 1930. c. ROSENBLAD 1,758,295

STEAM HEATED APPARATUS Filed Aug. 12, 1929 fig. i f1g 5 Patented May 13,1930 GUBT ROSENBLAD, F SUNDSVALL, SWEDEN STEAM-HEATED APPARATUSApplication filed August 12, 1929, Serial No. 385,369, and in SwedenAugust 25, 1928;

It is well-known to improve the efficiency of the heat transmissionsurfaces in steamheated apparatus by drawing 01f, together with thecondensate, a portion of the steam used for the heating and by returningsaid steamafter it has been separated from the condensateto the supplypipe to the steamheated apparatus or by utilizing it in other steamconsuming apparatus. It has been found that also a little quantity ofsuch steam flowing through will increase the efliciency of the heattransmission surfaces very much.

It is, however, also desired to reduce the temperature of the condensatedrawn off as much as possible to obtain the best efficiency possible inthe heating process. If the condensate, as stated above, is drawn offtogether with steam it has a temperature determined by the steampressure in the outlet tube, i. e. the temperature of saturated steam atsaid pressure. This temperature is, however, relatively high, and theefliciency of the process is, therefore, reduced to a correspondingextent. Experiments have shown that it is impossible, from an economicpoint of View, to cool the condensate by increasing the heattransmission surface, because the coefficient of heat transmission forthe cooling of the condensate in the last portion of the heattransmission surface is very low, so that a disproportionally largeadditional surface is required.

The condensate drawn off may certainly be used for pre-heating purposesor for other consumption purposes for which heat of low temperature maybe used and thus the'condensate is cooled. This is, for instance, oftenthe case in multiple effect evaporating appa- 40 ratus in which thecondensate from the evaporators is used for pre-heating the liquor to beconcentrated. It is, however, a wellknown matter of fact that the heattransmission from a medium in the liquid state is sub- 5 stantiallylower than that from the same medium, when it is in the gaseous state.The efliciency of the heat transmission surfaces in the pre-heater is,therefore, much lower than that of the surfaces in the apparatus proper.

oil the condensate at a temperature as low as possible. The inventionconsists, chiefly, in inserting between the sections a throttled passageor other pressure reducing means and after it a steam separator toseparate, from the condensate flowing from the preceding section, thesteam possibly flowing through as Well as the steam formed from thecondensate on account of re-evaporation, said steam being thereaftersupplied to the following section.

The throttled passage in combination with the steam separator causesformation of steam from the condensate again on account ofre-evaporation and thetemperature of the condensate is'in this wayreduced. The steam so formed together with steam flowing through, ifsuch steam is at hand, is in the steam separator freed from thecondensate and supplied to the following section in which a lowerpressure than that in the preceding section prevails. As the heattransmission from steam is considerably better than that from condensatea considerably higher efficiency in the heating surface of thesubsequent apparatus is obtained than would be the casevif thecondensate possibly mixed with steam flowing through was directlysupplied to the subsequent section.

The condensate from the steam separator may either be drawn off directlyby means of a condensate discharger of the usual type or be drawn off ina pipe passing by the following section and be incorporated with thecondensate flowing from the latter.

By use of the combination according to the invention the condensatealready formed is partially converted to steam on account ofre-evaporation and said steam together with excess steam flowing throughis utilized in a heat transmission surface at a lower pressure. The heatin the condensate can generally not be utilized in an economic manner aslon as it is absorbed in a liquid but'is according to theinvention'caused to be partially absorbed in steam and can, there ore,be utilized more easily. The final temperature of the condensate will,of course, depend upon the conditions of the special case but maygenerally be said to be about 100 C. Under particular conditions thetemperature of the condensate drawn off may bestill more decreasedby-use' of vacuum.

The invention may, preferably, be combined with the means for-regulatinthe-heat effect in'steam-he'ated apparatus desc ibed in my co-pending U.S. patent application Serial No. 320,694, filed November 20, 1928. Inaddition to the throttled passage and steam separator provided betweenthesections of the heat transmissionsurfaces according to the presentinvention a suitable pumping device is then provided in the steam supplypipe to the section having the lowest pressure. The suction pipe of saidpumping device is connected with the outlet pipe from the section havingthe lowest pressure and to said outlet pipe condensate mixed with steamis supplied from said section-through a throttled passage according to'my said copending U. S. patent application No. 320,694. The condensatefrom the section or sections having higher pressure may, preferably, besupplied to the same outlet pipe and is then caused first to pass anadditional throttled passage and, if desired, also a steam separator,which compensate for the drop-of pressure in the pumping device. In thesuction pipe of said pumping. device an air relief cock should also beprovided to remove all air present in the s stem.

Some em odiments. of the invention are illustrated in the annexeddrawings. Figs. 1 and 2 show a system according to the invention, inwhich the two sections of the heat transmission surfaces are placed inone and the same outer casing and the steam separator is constructed ascondensate discharger or is connected with the outlet pipe from the lowpressure section, respectively. Fi 3 shows the same system as that shownin ig. 2 but having three sections in series. Figs.

4 and 5 show a system according to' the in-' vention in combination, atthe low pressure section, with the means disclosed in my co- E ending U.S. patent application 320,694. In ig. 4 the sections are enclosed in oneand the same outer casing and in Fig. 5 in two separate casings, anadditional steam separator being provided in the system shown in saidlast-mentioned figure.

Referring now to the drawings 1 is a heating apparatus adapted forindirect steam heating by means of the heating element passing throughit. Said heating element is, by

means of a throttled passage 2, which may be of fixed area or ofadjustable area, divided into a high pressure section 3 and a lowpressure section 3", After the throttled passage a combined steamseparator and condensate discharger 7 having a float,, valve isprovided.

The live steam is supplied through the valve 4 and the condensate fromthe low pressure section is drawn off through a condensate'discharger 6having a float valve 5. The direc-' tions of flow are indicated byarrows.

The live steam supplied through the valve 4jfirst .passes the highpressure section 3*, and delivers heat while being partially condensed.The condensate together with the excess steam flowing through passesthrough the throttled passage 2 to the steam separator 7. Said excesssteam serves to remove the.

condensate preciptated onthe walls of the high pressure section 3" andthus to maintain the efliciency of the heat transmission at a highvalue, because the condensate, which has a poor heat conductivity wouldotherwise decrease the heat transmission.

. The steam separated in the steam separator 7 which consists ofsuchsteam flowing through togetl erwith steam formedon ac- .count ofare-evaporation from the condensate is then supplied to the low pressuresection- 3 and the condensate from the low livers heat to thesurrounding liquid in the low pressure section forming still morecondensate which has the-same temperature as that of the remainingcondensate from the the high pressure section. The condensate flowingfrom the' two sections has thus one. and the same temperature determinedby thepressure prevailing in the low pressure section and saidtemperature -.is lower than would be the case if the throttled passageand the steam separator had not been provided.

Instead of the combined steam separator and condensate discharger 7shown in Fig. 1' a steam separator 8 may be provided after the throttledpassage 2, 'as shown in Fig. 2, and the condensate therefrom be drawnofi through a pipe 9 passing by the low pressure section 3" anddischarging into the condensatedischarger 6 of the low pressure section.

,In Fig. 3 an embodiment is shown having three pressure stages in theheater. Three therein flows to the intermediate pressure section 3"while the condensate is drawn off through a pipe 11 having a throttledpassage 12 to a second steam separator 13 with which the intermediatepressure section 3 also communicates via a throttled passage 2. Afterthe steam and condensate have been separated in said steam separator 13the steam flows into the low pressure section 3 while the condensateflows through a pipe 14 to the condensate discharger 6 having the floatvalve 5. From said discharger 6 the condensate formed in the lowpressure section 3 is also drawn oft.

In Fig. 4 one embodiment of the invention in combination with means forrcgulat ing the steam flowing through the low pressure section accordingto my co-pending U. S. patent application No. 320,694 is shown. In anapparatus of the same design as that illustrated in Fig. 2 two throttledpassages 15 and 16 are inserted one in the condensate outlet pipe fromthe low pressure section 3 and one from the steam separator 8 to thecondensate diseharger (S. The steam chamber of said last-mentioneddischarger is connected with the steam supply pipe 19 to the lowpressure section 3 by means of the suction pipe of a pumping device, forinstance, an injector 17, which is operated by the steam flowing in thepipe 19 from the steam separator 8 to the low pressure section. In thesuction pipe 17 of the injector 17 an air escape cock 18 is inserted toremove the air present in the system.

The steam coming from the steam separator 8 operates the injector l7 andsuffers on account thereof a little drop of pressure and flows togetherwith the excess steam sucked by the injector from the outlet of the lowpressure section into the inlet of said low pressure section through thepipe 19. The circulation of steam thus brought about renders a highefliciency of the heat transmission also in the low pressure section 3because the condensate is rapidly removed from the heat transmissionsurfaces thereof.

Fig. 5 shows a modification of the combination illustrated in Fig. 4.The high pressure section 3 and the low pressure section 3 are here eachprovided in one portion 1 and 1 of the heating apparatus and a littlesteam separator 20 is inserted after the steam separator 8 to separatethe steam formed by the re-evaporation caused by the throttled passage16. Said re-evaporated steam is sucked by the injector 17 which in thiscase generates a vacuum while the remaining condensate flows to Y thecondensate discharger 6 and is pumped off by the pump 21 which may alsomaintain a vacuum.

In addition to the embodiments illustrated in Figs. 1-5 of the drawingsalso other embodiments are possible which fall Within the scope of theinvention. Any number of cooperating apparatus and any number ofsections of'the heating element may be used. If it is desired to reducethe temperature of the condensate discharged from the system below 100C. the last section is caused to operate in vacuum by substituting avacuum pump and a condensate pump 21 for the injector and the condensatedischarger, respectively.

The throttled passages between the sections of the heating elements may,if the pressures and steam quantities in the plant are constant, besimple throttling discs of constant area, or common steam valves, if itis desired to regulate the pressure to a certain value. If, 011 thecontrary, the pressures and steam quantities vary in the systemautomatic steam pressure reducing valves are, preferably, used, whichmaintain at constant values the reduced steam pressure and consequentlyalso the temperature of the condensate drawn ott.

lVhat I claim is:

1. In a system comprising steam-heated apparatus having the total heattransmission surface divided into more than one section connected inSeries a throttled passage and after it a steam separator in seriesbetween all ofthe sections.

2. In a system comprising steam-heated apparatus having the total heattransmission surface divided into more than one section connected inseries a throttled passage and after it a steam separator in seriesbetween all of the sections, and a condensate pipe connecting each ofsaid'steam separators with the following one. 1

3. In a system comprising steam-heated a pparatus having the total heattransmission surface divided into more than one section connected inseries a throttled passage and after it asteam separator in seriesbetween all of the sections, a condensate pipe connecting each of saidsteam separators with the following one, and a condensate pipeconnecting the last of said steam separators with the outlet pipe fromthe'last of said sections.

4. In a system comprising steam-heated apparatus having the total heattransmission surface divided in more than one section connected inseries a throttled passage and after it a. steam separator in seriesbetween all of the sections, a pumping device, a suction pipe betweenthe outlet pipe from the last of said sections and said pumping device,a throttled passage in said outlet from'the last section before saidsuction pipe, a pressure pipe between said pumping deviee and the inletpipe of said last section, and an additional throttled passage in theoutlet pipe from the last previous section.

5. In a system comprising steam-heated apparatus having the total heattransmission surface divided into more than one section after it a steamseparator 1n serles between tled passage in the condensate outletconnected in series a throttled passage and after it a steam separatorin series between. all of the sections, a pumping device, a suction pipebetween the outlet pipe from the last of said sections and said pumpingdevice,

a throttled passage in said outlet from the last section before saidsuction pipe, a pressure pipe between said pumping device and the inletpipe of said last section, an additional throttled passage in thecondensate. outlet pipe from the last previous section,'and a littlesteam separator immediately after said additional throttled passage. 2

6. In a system comprising steam-heated apparatus having the total heattransmission last section.

vious section, a little. steam separator immediately after saidadditionalthrottled passage, and means for generating vacuum in said Intestimony whereof I have signed my name.

oUR'r ROSENBLAD.

surface divided into more than one section connected in series athrottled passage and after it a steam separator in series between allof the sections, a pumping device, a suction pipe between the outletpipe from the last sectionand said pumping device, an air escape devicein said suction pipe, a throttled passage in said outlet from the lastsection before said suction pipe, arpressure pipe be; tween said pumpingdevice and the inlet pipe of said last section, and an additionalthrotconnected in series a throttled passage and after it a steamseparator in series between all of the sections, apumping device, asuction pipe between the outlet pipe from the last of said sections andsaid pumping device, a throttled passage in said outlet from the lastsection before said suction pipe, a pressure pipe between said-pumpingdevice and the inlet pipe of said last section, an additional throttledpassage in the outlet pipe from the last previous section, and means forgenerating vacuum in said last section.

9. In a system comprising steam-heated apparatus having the total heattransmission surface divided into more than one section connected inseries a throttled passage and all of the sections, a pumping device, asuction pipe between the outlet pipe from the I last section and saidpumping device, an air escape device in said suction pipe, 2. throttledpassage in said outlet from the last section before said suction pipe, apressure pipe between said pumping device and the inlet pipe of saidlast section, an additional throttled passage in the outlet pipe fromthe last pre-

